1. Field of the Invention
This invention relates to a bioluminescent sensor system and in particular to a detection system including at least one sensor for identifying specific vapors, with fluid paths for alternately introducing fluid sample for testing, and humidified fluid for conditioning the sensor and its environment.
2. Description of the Prior Art
In fluid or air sampling systems in use with bioluminescent sensors where the sensor is typically isolated, except during short sampling or humidifying intervals, such as disclosed in U.S. Pat. No. 3,370,175 entitled Toxicant Detector for inventors A. L. Jordan et al, issued on Feb. 20, 1968 and assigned to the owner of the present invention, sensitivity of the detection medium may be affected. This can be caused by a loss in moisture from the agar medium or other suitable substrate, on which the detection medium, including the luminous culture comprising microorganisms such as bacteria or fungi, are grown. Air sampling systems which provide only for sample fluid or air continuously blowing across the sensors, if not otherwise compensated for, can be the cause of unsatisfactory results since the sensor loses moisture and can respond to humidity changes, and the total luminescence and reactivity of the culture may be changed and generally decreased. Air sampling systems, where the bioluminescent sensor is constantly exposed to the atmosphere being tested, cause the sensor to become equilibrated to the specific gas under test and the biosensor will not respond to that gas unless it is above the ambient concentration.
Typical solutions to these humidification problems involve so-called stop-flow methods where the air flows across a sensor and is turned on and off at a rate dependent upon the frequency of sampling and in-line humidification where the sample passes through a humidifier. However, the first solution has drawbacks in that the bioluminescent sensor detector also responds to changes in humidity and air flow thereby disturbing it and causing it to react to disturbances other than that of the specific gas under investigation. Drawbacks with respect to the latter configuration are the loss of sample in the humidifier and the decrease of response to a specific vapor if low levels are already present in the environment.
These sensor microorganisms when cultured are grown under conditions of substantially 100% humidity. Therefore, sensor viability and sensitivity is maximum at high humidities. In addition, when subjected to varying humidity and fluid flow conditions, its response is affected.